1. Field
The present disclosure relates to a fuel cell.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell includes a membrane electrode assembly (MEA), in which an anode electrode is disposed on one side of a solid-polymer electrolyte membrane and a cathode electrode is disposed on the other side of the solid-polymer electrolyte membrane. The solid-polymer electrolyte membrane is made from a polymer ion-exchange membrane. The MEA and a pair of separators, sandwiching the MEA therebetween, constitute a power generation cell (unit cell). Several tens to several hundreds of such power generation cells are stacked and used, for example, as a vehicle fuel cell stack.
In a typical case, a fuel cell has a so-called internal manifold structure for supplying a fuel gas and an oxidant gas, each of which is a reactant gas, respectively to anode electrodes and cathode electrodes of power generation cells that are stacked. The internal manifold structure includes a reactant gas inlet manifold and a reactant gas outlet manifold, each extending through the power generation cells in a stacking direction in which the power generation cells are stacked. The reactant gas inlet manifold and the reactant gas outlet manifold (which, hereinafter, may be collectively referred to as a reactant gas manifold) are respectively connected to an inlet and an outlet of a reactant gas channel, through which the reactant gas is supplied along an electrode surface.
In this case, the reactant gas manifold has a comparatively small opening area. Accordingly, in order to allow the reactant gas to smoothly flow through a reactant gas channel, it is necessary to provide buffer portions (an inlet buffer portion and an outlet buffer portion), for diffusing the reactant gas, in the vicinity of the reactant gas manifold.
For example, Japanese Patent No. 5197995 describes a fuel cell in which a reactant gas can be uniformly supplied to the entirety of a reactant gas channel from a reactant gas manifold through a buffer portion.
In this fuel cell, a separator has the reactant gas manifold, through which the reactant gas flows in a stacking direction, and the buffer portion, which connects the reactant gas manifold to the reactant gas channel. The buffer portion includes a first buffer region near the reactant gas manifold and a second buffer region near the reactant gas channel. The first buffer region (deep buffer) is deeper than the second buffer region (shallow buffer) in the stacking direction. Accordingly, it is possible to uniformly and reliably supply the reactant gas to the entirety of the reactant gas channel from the reactant gas manifold through the buffer portion.